Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
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        BNP Test, Blood
      

URGENT!: an abrupt FDA recall of our Alere (Biosite) BNP test products in Dec. 2012 resulted in at least temporary suspension of any action-value parameters, below. We have urgently had to substitute a new test, NT-pro BNP6. It is not affected by Nesiritide6. "Normal" is less than 125; at less than 300, CHF is doubtful but not excluded; greater than 300 and less than 1,000 is a borderline range; greater than 1000 is biochemical evidence of CHF; and greater than 10,000 means severe CHF is likely6. However, the levels can be disproportionately high...out of kilter with clinical info...in dyalysis patients (or those with serious renal compromise). Increasing levels suggest worsening; decreasing levels suggest improvement6. A normal level can be extremely useful to more or less rule out CHF.

Note: specimen must not be older than 4 hours from time of phlebotomy. This EDTA-anticoagulated plasma-only test for brain (beta-type) natriuretic peptide (BNP) can be  run on such as the desk-top Triage system or a fluorescent system. [the vendor]  

BNP is elevated when increased wedge pressure or "stretch"...stress...is placed on one or both cardiac ventricles...whether yet causing symptoms or not. The test module was created for easy & early detection of new cases or relapses of congestive heart failure (CHF) in patients with shortness of breath (SOB), onset of cough, or abnormal chest X-ray. It is estimated that more than 5,000,000 US citizens suffer CHF. Elevations will also occur in systemic hypertension (if it is causing chronic "stretch" leading to ventricular enlargement). Uncomplicated COPD and bronchiolitis/pneumonia do not elevate BNP. However, pulmonary emboli sufficiently obstructive to produce increased ventricular stretch will elevate BNP.

BNP identifies patients with cardiac "pump dysfunction", stretch, or stress. BNP is elevated in both diastolic (diabetic effect, toxic effect, or drugs that affect myocardium...such as chemotherapy drugs) and systolic dysfunction (echocardiogram abnormal only in systolic dysfunction) AND even when ejection fraction is preserved5!

ER use: When accurately deployed, the test helps in every ER case of shortness of breath of seriously-uncertain etiology. It helps settle the classical patient-case disputes between pulmonologists and cardiologists as to whether CHF is any of  the cause of the symptoms/abnormal chest X-ray, or not.  The half-life of BNP is short; so, to prove proper CHF treatment response, BNP levels can be followed for expected declines in about 2 days. We've sent this test out to reference labs as of12/2002; we were in the implementation phase for on-site testing at the LMC main lab as of 19 May 2003 (in use as of mid-June 2003).

Although ER doctors must take many factors into account in the diagnosis of CHF, a BNP of less than 100 pg/mL makes CHF dyspnea highly unlikely (although some cases with mild dyastolic dysfunction but preserved ejection fraction even have a BNP no higher than about 405), 100-400 is indeterminate, and greater than 400 gives a 95% likelihood of CHF2 (a cardiac pump dysfunction). When greater than 500, CHF (a cardiac pump dysfunction) is highly likely. From another perspective, a rule of thumb is that a level >100 is abnormal.

For CHF inpatients: It may prove to be a critical safety factor to repeat BNP prior to discharge and be sure that it has improved concordantly with sign & symptom improvement.

For asymptomatic office cardiac assessment screening: those with elevations (=/>12.8 for men & =/>15.8 for women) have an increased risk of death3. A look at multiple markers also by Dr. Wang4.

References:

  1. CAP Today, March 2002 & April 2004 via CAP website
  2. Bhalla V, et. al., Biomarkers of CHF, Advance/Laboratory, April 2004. (EBS's office)
  3. CAP Today Dec. m2007 ref. to Wang T, et. al., NEJMed 350:655-663, 2004.
  4. CAP Today Dec. m2007 ref. to Wang T, et. al., NEJMed 355:2631-2639, 2006.
  5. Bursi F, et. al., "Systolic and Diastolic Heart Failure in the Community", JAMA 296(18):2209-2216, 8 November 2006.
  6. Carter JB, Director of Clinical Labs @ LMC, memo to ER, etc, Dec. 2012.
(posted May 2002; latest update 30 September 2008; urgent addition 20 April 2013)
 
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